code: def simple_index(self) -> CategoricalIndex:
      return CategoricalIndex(
          list("aabbca"), categories=list("cab"), ordered=False
      )
  
imports: import numpy
  import pytest
  from pandas._config import using_pyarrow_string_dtype
  from pandas._libs import index
  from pandas._libs.arrays import NDArrayBacked
  import pandas
  from pandas import Categorical, CategoricalDtype
  import pandas._testing
  from pandas.core.indexes.api import CategoricalIndex, Index
label_desc: Use image node_id 1 for calling the TestCategoricalIndex obj's underlying member method code with example usage: obj.simple_index() and returns: CategoricalIndex